1. Technical Field
The subject matter described herein relates to non-reciprocal devices.
2. Background Art
A non-reciprocal device is a device in which signals traveling from a first port of the device to a second port of the device behave differently than signals traveling from the second port of the device to the first port of the device when the device is under electrical bias. Similarly, signals traveling from the first port of the device to a third port of the device behave differently than signals traveling from the third port of the device to the first port of the device. Examples of non-reciprocal devices include, for example and without limitation, circulators and isolators. A circulator exhibits non-reciprocal behavior in that a signal entering a given port of the circulator is transmitted to the next port in rotation and not to other ports of the circulator. For instance, in a three-port circulator having first, second, and third ports, a signal applied to the first port comes out of the second port (and not out of the third port); a signal applied to the second port comes out of the third port (and not out of the first port); and a signal applied to the third port comes out of the first port (and not out of the second port). Signals that are transmitted in accordance with the rotation of the circulator as described above typically experience a 1 dB loss; whereas, signals that are transmitted in the opposite direction (i.e., counter to the rotation) commonly are attenuated by 20 dB or more. The non-reciprocal behavior of a circulator is generated when a magnetic field interacts with a ferrite (e.g., garnet). An isolator may be formed by connecting a port of a circulator to a reference voltage through a resistive component. For instance, the resistive component may be a resistor (e.g., a 50 ohm resistor or an element of similar impedance).
Wireless communication devices, such as those used in telecommunication systems (e.g., cellular phones and smart phones), are devices that transmit and receive communications using antennas. Limited solutions for utilizing circulators in communication devices have been disclosed in the art. One example is described in Jeffrey L. Young et al., “Bandwidth Optimization of an Integrated Microstrip Circulator and Antenna Assembly: Part 1,” IEEE Antennas and Propagation Magazine, Vol. 48, No. 6, pp. 47-56, December 2006 and Jeffrey L. Young et al., “Bandwidth Optimization of an Integrated Microstrip Circulator and Antenna Assembly: Part 2,” IEEE Antennas and Propagation Magazine, Vol. 49, No. 6, pp. 82-91, February 2007. In this work, Young et al. stated that circulators may be designed with impedance matching for antennas in communication devices. However, the current state of the art lacks solutions for actively tuning circulators during operation based upon changing circuit parameters. The current state of the art also lacks solutions for efficient, large-scale manufacture of circulators.
The features and advantages of the disclosed technologies will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.